We write the product 5×4×3×2×1 as 5! and call this factorial 


five. 


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Similarly <i>n</i>! = <i>n</i>(<i>n</i> &#8722; 1)(<i>n</i> &#8722; 2) ... 2&#x00D7;1. Investigate the number of divisors of n!.